EXPLORATION OF GEOTHERMAL ANOMALY OF URACH WITH A VIEW TO ECONOMIC UTILIZATION AND FRAC STUDIES IN THE EXTENDED RESEARCH BOREHOLE URACH, 1977 - 1982
Until recently the exploration of the geothermal anomaly of Urach (Swabian Alb. SW-Germany, south of Stuttgart) was limited to water bearing sedimentary horizons, mostly in the Upper Muschelkalk of the Middle Triassic. By means of the research borehole Urach (deep well Urach 3) at the centre of this anomaly, exploration was extended to the basement for the first time. Originally the well was planned to a depth of 2100 m or 2500 m but the final depth is 3334 m below surface (2908 m below mean sea level) with a 1732 m penetration of basement. At a drilling diameter of 8-1/2-inch in this research-well, 7-inch casing was landed and cemented at a depth of 3320 m. The well head end-flange is suitable for a well head pressure up to 700 bar which is expected for the later frac operations. The following mean results are: There are no severe problems when drilling through basement for the hot dry rock concept. Average drilling progress is expected to be 1.5-2.5 m/h. Best tools when drilling in the basement were medium hard insert bits (type 3 JS-5 JS, J 44 and M 88) for drilling and very hard diamond bits (type C 24) for coring. In spite of rock tensions the uncased hole (up to 1500 m) offers no casing problems. A final casing is necessary because of decomposed zones. The Urach 3 well has achieved all its planned targets, at least from a technical and geological point of view. It is believed, therefore, that this is an important contribution to a future large-scale technical utilization of geothermal energy stored in the crystalline basement.
Bibliographic Reference: EUR 9123 DE (1984) MF, 733 P., BFR 960, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989122034900 / Last updated on: 1987-01-01
Available languages: de